Add time:08/29/2019         Source:sciencedirect.com

We show that for each k≥4 and n>r≥k+1, every n-vertex hypergraph with edge sizes at least r and no Berge cycle of length at least k has at most (k−1)(n−1)r edges. The bound is exact, and we describe the extremal hypergraphs. This implies and slightly refines the theorem of Győri, Katona and Lemons that for n>r≥k≥3, every n-vertex r-uniform hypergraph with no Berge path of length k has at most (k−1)nr+1 edges. To obtain the bounds, we study bipartite graphs with no cycles of length at least 2k, and then translate the results into the language of multi-hypergraphs.

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